clang-format: [JS] Making arrow function wrapping more consistent.

Before:
  someFunction(() =>
               {
                 doSomething();  // break
               })
      .doSomethingElse(  // break
          );

After:
  someFunction(() => {
    doSomething();  // break
  })
      .doSomethingElse(  // break
          );

This is still bad, but at least it is consistent with what we do for other
function literals. Added corresponding tests.

llvm-svn: 238736